SMALL-INTESTINAL STROMAL TUMORS WITH SKEINOID FIBERS IN NEUROFIBROMATOSIS - REPORT OF 4 CASES WITH ULTRASTRUCTURAL-STUDY OF SKEINOID FIBERSFROM PARAFFIN BLOCKS

Small intestinal stromal tumors (SIST) with skeinoid fibers (SF) are r eported in four patients with neurofibromatosis. SF appeared as interc ellular eosinophilic globules that stained positively on periodic acid -Schiff stain and bluish on Masson trichrome stain, like those reporte d previously. Electron microscopic confirmation of SF was carried out on tissue retrieved from paraffin blocks, which revealed diagnostic ul trastructural features of SF. The association of SIST with SF and neur ofibromatosis enhances the diagnostic value of SF as a marker of neuro genic spindle cell tumors. This study also underscores the importance of electron microscopy for differentiation of SF from pseudoskeinoid s tructures, which may mimic SF on light microscopic examination.